


Sugared Sweetness on My Tongue and Fang

by damnedxfate



Category: Undertale (Video Game)
Genre: Adorable Papyrus (Undertale), Alternate Universe - Swapfell, Alternate Universe - Underfell, Alternate Universe - Underswap, Alternate Universe - Vampire, BBQTacos - Freeform, Bitten againstwill, Blood Drinking, Fontcest, Frottage, LEWD, M/M, Magic Drinking, No actual sex, Puppyberry, Sibling Incest, Size Difference, Size Kink, Swapfell Papyrus - Freeform, Swapfell Sans, Underfell Papyrus, Underswap Papyrus, Underswap Sans, Vampire!Slim, dub-con, innocence kink, yandere!Slim
Language: English
Status: In-Progress
Published: 2017-07-27
Updated: 2018-08-31
Packaged: 2018-12-07 20:19:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,765
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11631153
Author URL: https://archiveofourown.org/users/damnedxfate/pseuds/damnedxfate
Summary: Slim can't control himself anymore around his brothers sweet blue counterpart. He has to taste him.





	1. Chapter 1

**Author's Note:**

> Do not read this if you are younger then 18.

He was known by many names throughout his life. From Papyrus to Slim, from mutt to being affectionately called Puppy by the innocent skeleton sleeping before him. Since Slim was young he craved the magic of other monsters. Feeling an all-consuming hunger that chipped away at his self-control.   
  
Black, his younger brother, had the most satisfying magic. Rich, dark, it would slide over his conjured tongue and down his throat. The blood and magic would pour thickly down, cascading over his soul where it was absorbed ravenously. Black was a treat to feed from and usually it quenched his thirst, but not lately.   
  
Since meeting their alternative selves none had caught his attention much. Even the red version of his brother who was so similar to Slim himself nor the sweet innocent version of Slim. The “Original” Papyrus whom showed so much spine and leg, whom oozed an aura of delectable scents. Had no effect on him. Then he met the Swap brothers and it took his own brother dragging him away in a staged fit of anger so that he would not attack that innocent blue skeleton.  
  
Their first meeting had to be cut short. When he had been dragged away, he is ashamed to admit he had pinned his brother down and bit into his unguarded neck with a ferocity he hadn’t felt since long ago when his fangs were new and all were prey. He had barely pulled himself off his moaning, twitching sibling.  The punishment afterward was brutal and the memory still lances across his body like fire.  
  
Getting to know the skeleton sweetly nicknamed Blueberry had done nothing to calm his lust to taste him. He wanted nothing more to take that precious little being and trap him alongside Slim’s own brother.  Keep them clean and well kept. Fed in excess so they had plenty of magic for him to drain. Their precious little bodies laid bare before him.  
  
Wiping the drool from his mouth, Slim licked his sharp fangs. Eyes glowing like demon’s fire. He had planned this for weeks. His own brother was passed out after one of their sessions. Body satisfied and magic drained. Blue’s brother off most likely getting drunk.  
  
‘ _He doesn’t deserve you, precious. I would never leave you alone._ ’ He thought listening to the tiny  
“Mwehs” Blue let out occasionally. A whisper of a smile adorned his innocent face. He was having a good dream. Slim almost felt bad to interrupt it, but if he didn’t satisfy himself now he himself even feared what he might do in the future.  
  
Climbing onto the bed he pulled the blanket down to Blue’s waist. The action woke him from his slumber.  
  
“ Uuu..uh..m-mweh? Ppuppy? W-what are you doing in my room? WAIT! Ge-get off! What are you-?!”   
  
The groggy voice and hazed starlit eyes woke the beast inside him. His magic roared to the surface. His fangs grew to their last length hooked slightly back to hold struggling prey. Eye lights blew wide covering his entire sockets. The dark orange magic fiercely licking out the side of his face and he pushed his allure out ward, focusing it all on the helpless victim below him.  
“Y-your eyes are…g-glowing…wh-what’s happening to meee? I can’t move. I don’t, I don’t understand” Tears began to form at the corner of bright eyes. His struggling arms that had rose to press against his attacker’s chest slowly falling limp against the bed.  
  
“Ssh baby Blue. You don’t need to be afraid. You made me a promise remember? That if I ever needed anything to come to you, that you would gladly help me, and I’m so incredibly  **hungry** ” Inhaling deeply, Slim felt his tongue forming in preparation to finally taste, to finally sample and bite and swallow that sweet ambrosia laying before him supine and weak.  
  
“you’re hungry…? I don’t-AH! don’t take my shirt off!” Whining his little Blue tried to protest and resist him. Tossing the offending garment to the side Slim took in the pale expanse before him. Almost an exact replica as his brother’s ribs. Blue’s ribs were lacking the subtle off-white marks of old bite scars and cracks from a harder fought life. Now was not the time to admire, it wouldn’t do for the neglectful brother to come home.  
  
Purring he leaned forward burying his head between head and collar bone. Inhaling the scent of soft vanilla and sugared sweetness. Unable to resist tasting the bones before him further teasing himself, he laved those sweet little vertebrae liberally.  Before opening his mouth wide, positioning his fangs where he could puncture them most deeply. It was time to finally satisfy his blood lust.  
  
“M-my neck...stop, stop licking iiit” Blue whimpered head forced back. Staring at the plastic glow-in-the-dark-stars he and his brother had placed on the ceiling of his room so many years ago.   
  
“Aaah ah…OW! Ooow, it hurts! P-puppy Uuun” Whining Blue began to cry out. It felt like two knives had been pressed into his neck. Burning pain raced through him as he felt a strange force, pulling something from his soul.   
  
The pain was gone as quick as it came and a pleasant warmth began to spread from the bite. Blue could hear Slim moaning, could feel the vibrations. The tongue securely wrapped around the bitten vertebrae coupled with a wet warmth that trickled out slowly. Blue could hear the mouthfuls Slim was gulping down. His body felt weaker but craved more. Darkness grew around him.  
  
‘ _I can’t feel my body. I’m so t-tired but it f-feels so good. M-my minds going all…fuzzy_.’ Before the blessed feeling of unconsciousness took him Blue gazed once more at those glowing stars. ‘  _Papy…ah…Papy…help meee’_  
  
Feeling the body below him go fully limp, Slim forced himself to relinquish his bite. Licking up any spilled remains he pulled back straddling the much smaller skeleton. Precious little Blue looked as if he was sleeping, as if nothing had transpired. His tiny chest shakily rose and fell shallowly, his face dusted faintly blue.  Upon his neck were to wide open punctures. While his brother walked their world bearing his mark, covered with his bandana of course, it would be unwise to leave any evidence.  
  
Pressing his hand to the bite, he healed the wound. Besides some tenderness, there was no trace. Blue would have no memory of that night. Perhaps flashes as if he had dreamt it. Dreamt a copy of his brother leaning over him, touching him, biting him. Smirking he wondered how Blue would handle their next interaction. Believing he had a wet dream of him.   
  
Standing Slim picked up the discarded shirt and redressed Blue. Tucking him firmly into bed he pressed a gentle kiss to his forehead. His hunger was sated, for now.  
  



	2. Chapter 2

**Summary for the Chapter:**

> Unexpected surprises couples with unending hunger

**Notes for the Chapter:**

> I didn't intend to continue this for a long time but I did toy with the idea. Originally the sequel if any was going to be just one long chapter but I decided to do a multi chapter fic so as not to overload myself and deviate a bit by adding more plot!

No one came this deep into Snowdin Forest. The gnarled trees and biting winds as unwelcoming as the denizens that lived in the unforgiving landscape. So no one was around to see the debauched Sans of Swapfell dangling limpy from his brother’s arms. They wouldn’t see his body jolting from each punishing thrust or hear the lewd slurps as Slim drank his fill from the deliriously babbling skeleton.   
  
Slim had been voracious lately. Even now with his brother’s magic nearly drained to the point of unconscious he needed more. Before, Black’s blood had been more than enough to keep him content but, no longer. His hunger had grown exponentially the moment they learned of the multiverse and Slim laid eyes on the little blue skeleton. His mind nearly lost the moment he pinned the sleepy body under him and sank his fangs deep into bone. His love for his brother spreading to the innocent counterpart easily. The pull powerful but confusing.   
  
Since then no matter how much he drank from his brother or snuck into the hyperactive skeleton’s room over in Underswap he still felt so hungry. His non-existent stomach curling in on itself from starvation. Even now he felt hollow inside. His middle an echoing chasm.   
  
“Mutt..hahn..can’t…” the whimpered words were more air then sound. Considering how much Slim had drained already and how many orgasms he had pulled from the smaller body, Black probably had nothing more to give.

Regretfully, Slim pulled out of the pulsing magic that dispelled as soon as it was no longer in use. The inside of the pelvis still blushed a weak, struggling purple. Slim was still rock hard but could tell Black was slowly losing consciousness in his arms. The stuttering gasp mellowing into slow even breathes of exhaustion spawned sleep.   
  
Regretfully, Slim tucked his still pulsing length away. “I got you baby bro. Let's go home” sweeping Black up bridal style, he short cut them home. A quick CHECK showed him Black was fine physically just exhausted, not surprisingly. Propping Black up against the side of the tub for a moment, Slim got the water to slowly fill the basin. Submerging Black into the waist high warm water, Slim caressed the still faintly rattling bones. He knew he had to corral himself but he felt like he just couldn’t stop. Hungry for magic or sexual gratification it didn’t matter. He needed more of not only his sibling but from Blue to.   
  
“Sorry baby bro”   
  
An apology to cover so many things. Sorry to have drained him. Sorry for his hunger. Sorry that later he would leave Black alone snuggled in bed while Slim went into the basement and snuck to Underswap. Sorry that he would spend the night pinning the gyrating look alike to the bed while he drank more. Sorry that he would keep doing this over and over.   
  
“I will find a way to fix this” He didn’t take this lightly. He would find a way to fix this. He would have them both. He would stop his hunger somehow before he killed one of them trying.

* * *

“Puppy, puppy, puppy. Oh Stars haaaaahn...me too please pu-aahpy” Blue no longer needed to be subdued with Slim’s magic nor hypnotism. He probably still thought these midnight interactions were fantastical dreams that left him sated and drained in the morning. But he welcomed Slim with open arms and a bared neck each time. They never had sex. Their clothes stayed on each time but their bodies rocked to the ecstasy of the feeding. The bed creaking softly under their undulating bodies. Blue’s lustful cries just loud enough for Slim to hear but not nearly enough to wake Stretch in the next room.  
  
Slim was already taking great gulps of magic while he ground his rigid cock against the soaking wet mound under him. Their clothes sticking to the summoned magic like a second skin. Small hands clawed frantically at his back, yanking at him or pulling him closer intermittently. Slim didn’t care about Blue’s garbled moans, or the twitching cunt below him. He just wanted more of the sweet periwinkle magic flooding his mouth, running over his tongue like a soothing balm. The cramps slowly diminishing until he began to feel warm and sated. Nothing dragging him out of his meal until he felt a sharp sting where Blue’s mouth was nestled against his cheek.   
  
The sting felt almost like the love nips Black would give him that would bruise and bleed. Blue did not have teeth nearly as sharp as Black’s. Slim had seen enough of Blue’s teeth, the smaller skeleton was always smiling, to know they were blunt like any other taleverse monster. The shock of pain and the curiosity was enough to drag him away from his meal.   
The sight that greeted him snapped the world into startling focus but this was not at all what he would expect.   
  
Blue’s mouth was wide open while he struggled to pull in unneeded air. The false moonlight glistening over tiny nubs nestled on each side of his upper jaw. Nubs that should not be there. Nubs that looked eerily like Slim’s when his hunger first started. Blood dripped slowly down Slim’s cheek from the newly opened wound. Nubs apparently already sharp enough to pierce bone.   
Even more startling was the bright glowing eyes that bore into his soul. Normally, Blue’s eyes were the color of his magic. Soft shades of blue with glowing yelling stars, or hearts when Slim fed, now they glowed as if a fire burned inside his skull. The colors shifting eerily making the shadows in the room stand out in a starker contrast. Orange and Blue mixing in hellish light. Slim couldn’t pull himself away from those eyes even when the dainty hand dabbed at the blood still flowing sluggishly from the wounds Slim had forgotten to heal. He could only blink in shock, slack jawed, when Blue moaned after he stuck the phalanges coated in his own magic into his mouth. Slim still tightly pressed against Blue’s magic could feel it tremble and clench in orgasm at the act.   
  
“Well, fuck me sideways. Nyeh heh heh looks like you have a bit more common with me that you do my baby bro. Don’t you Blue?” Slim broke free from his stupor with a barely muffled cackle. Maybe this could be a solution to his problem? Maybe his dream of having sweet little Blue and Black in his bed could come true? Black was aware that Slim occasionally fed from other monsters. Usually it was criminals Black himself sent Slim after. He didn’t know that Slim was partaking of Blue nearly every night. Black was all for responsibility and well it wouldn’t be proper for Slim to let his fledgeling run around unaccounted for, right?   
  
His planning was halted when Blue started to crawl out from under him in a determined way. “No, no baby Blue. Gotta wait right here until I figure this out” Pinning the flailing body under him, Slim stuck his wrist in between Blue’s parted jaws. Hissing when Blue clamped down, suckling at the newly opened wound like a kitten at its mother’s teat.   
Gaster had warned him long ago before he was scattered into the void. That if Slim was ever fortunate or perhaps unfortunate enough to find someone else like him and converted them. It was Slim’s responsibility to care for the new fledgeling. Find the source of their hunger, bring them into the fold.   
  
For Gaster the fold was his fellow scientist. A group that held great sway over the comings and goings in the underground.   
Slim wasn’t that ambitious. For him his fold would be his mates, his harem, his escape from starvation.   
  
He needed to know who was it little Blue hungered for. Slim craved Black with every bit of his being. Pulling his wrist away he whispered, “Tell me. Whose magic makes your soul scream?”   
  
His answer- “Papy”   
  
Slim could make this work.

* * *

  
_“I actually… knew… it wasn’t a dream, not since after the first time. Sorry Puppy for lying” Blue admitted to them. They had invited him over the next day under the pretense of the Sanses having a training session. In all actuality it was for Slim to confess the truth. Well the truth to Blue._   
_Slim had already told Black everything that same night after he left Blue asleep on his mussed bed and came home to an irate sibling glaring him into submission._   
_The verbal and physical beatdown was more than enough to awake his interest but the near murderous aura raising off Black kept him demure._   
  
_At the confession, Black had no choice but to lean back and eye his counterpart appraisingly. Perhaps he had dismissed the other as innocent too easily. Not only had it known Slim was feeding from him, but had taken sexual gratification from the act. Even know while Blue’s body spoke of embarrassment there was a telltale glow slowly building in the dark grey pants. Very interesting._   
_In his sweep he noticed the subtle changes to the other Sans. The barely there fangs, unnoticeable unless one was actually looking for them, a deeper hue to the eyelights, and while subtle, the aura of a hungry predator. Very interesting indeed._   
_  
“Of Course you wouldn’t be fooled by this mutts shenanigans” Black followed his declaration with a nudge to his side where Slim kneeled bound in submission. The first part of his punishment, surely. There was no way Black was done with him yet. (he hoped there was more)_

_“It seems plans must be adjusted and rules laid out. This is what we will do…”_   
_  
Slim whined hungrily as they planned_

**Notes for the Chapter:**

> let me know what you think!

**Author's Note:**

> Author’s note: i just wanted to point out that Stretch is NOT a neglectful brother. He is actually really loving and doting. Slim just takes brothering kind of far, he devotes his entire being to his Sans so anything less is neglectful in his book.
> 
> Also yes this is slightly dub-con. Slim wants to keep Black and Blue as his captives forever. He is a bit yandere in this he just loves them so much and wants to keep them for himself always.
> 
> This is based on a audio i made on my Tumblr of the same name. Do NOT follow me if you are younger then 18 i will block you.


End file.
